1. Field of the Invention
The invention relates to a micro-optic fiber device, and more particularly to the technology for coupling, disposing and slightly turning the respective component such as the optical processing element, the fiber collimators, and the coupling tubes, which constitute the micro-optic fiber device.
2. Description of the Prior Arts
The most popular approach to making a micro-optic fiber device is to make two fiber collimators separately and insert an optical processing element such as WDM filters, isolator cores, birefringent crystals of PM combiners, and circulator cores in between to form fiber optic WDM devices, fiber-in-line-isolators, fiber PM combiners, and fiber circulators respectively. In the conventional art the collimators are attached to the optical processing elements either using soldering (tin solder) or bonding (epoxy). Usually the outer housing of the above-mentioned collimators is made of metals, and the optical processing elements are attached to the first or the second collimator using epoxy bonding or soldering (to form so-called subassembly). The subassemblies based on fiber collimators are then aligned and fixed using soldering or epoxy bonding techniques.
Although widely used in the fiber component manufacturing, the above-mentioned processes are operator dependent. The acceptance rate of the final products is accordingly low and skilled workers are not easy to find.
The most important point is that because the optical processing elements are attached to the collimators directly using epoxy or soldering bonding, the epoxy will flow into the optical path of the optical processing element and then will influence the optical path to such an extent as to deteriorate the optical performance. Stresses need to be applied on the elements for aligning purposes in the case of soldering, therefore the devices built suffer from high thermal dependent loss and insertion loss. This step, to some extent, has become the bottleneck in manufacturing the micro-optic fiber device.
Besides the above-mentioned techniques, another approach, according to U.S. Pat. No. 6,185,347 for making wavelength division multiplexed (WDM) devices, uses a dual fiber collimator and a single fiber collimator. In the dual fiber collimator a WDM filter is first attached to the first GRIN lens using a thermal cued epoxy. The subassembly is then inserted into a glass tube and fixed using the thermal cured epoxy. A dual fiber pigtail is then aligned to the subassembly with lowest reflection insertion loss and connected to the glass tube subassembly using a second glass tube, which forms the dual fiber collimator.
In the single fiber collimator, the second GRIN lens and a single fiber pigtail are inserted in the third glass tube aligned to dual fiber collimator for the lowest transmission insertion loss and fixed with thermal cured epoxy. Finally, the dual fiber collimator and the single fiber collimator are aligned with the lowest transmission insertion loss and joined at the first and the third glass tube using thermal cured epoxy. Although simple, the approach does not provide devices with optimal reflection and transmission insertion loss.
For filter attachment in a WDM device, the industry is now widely adopting the direct attachment of the filter onto the GRIN lens. The process needs the operator to align the filter with GRIN lens under a microscope and then apply UV epoxy on the surrounding of the GRIN lens-filter interface to prevent the thermal-cured epoxy applied later from flow into the optical path and at the same time to glue them together. In the patent (U.S. Pat. No. 6,185,347), the epoxy is used in between GRIN lens and the filter and thus it is an epoxy-in-the-optical-path design that system manufacturers disfavor.
The present invention has arisen to mitigate or obviate the afore-described disadvantages of the conventional micro-optic fiber device.